System to calibrate on-die temperature sensor

ABSTRACT

A system may include biasing of diodes of a temperature sensor disposed in an integrated circuit die using a current from an off-die current source, generation of a voltage based on the current and a temperature of the integrated circuit die, and determination of a first temperature based on the voltage. Such a system may further include amplification of the voltage using an oscillator and a chopper stabilizer, determination of a first amplified voltage associated with a first state of the oscillator and a second amplified voltage associated with a second state of the oscillator, and determination of a third voltage based on the first amplified voltage and the second amplified voltage, wherein determination of the first temperature based on the voltage comprises determination of the first temperature based on the third voltage.

BACKGROUND

An integrated circuit (IC) die includes a semiconductor substrate andvarious electronic devices integrated therewith. It is often desirableto determine the temperature of these electronic devices duringoperation of the IC die. Conventional systems may determine thetemperature using a temperature sensor integrated within the IC die.

An integrated temperature sensor may be calibrated to account forprocess and other variations. In a typical calibration procedure, theentire IC die is subjected to a known ambient temperature in an attemptto “soak” the temperature into the die. An output of the temperaturesensor is then obtained, and a calibration factor is determined based ona difference between the ambient temperature and the output of thetemperature sensor. Such calibration may result in inaccuratetemperature measurements due to several factors, including a differencebetween the ambient temperature and the actual temperature of the dieduring calibration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an IC die according to some embodiments.

FIG. 2 is a diagram of a process to determine a temperature according tosome embodiments.

FIG. 3 is a schematic diagram of a calibration apparatus according tosome embodiments.

FIG. 4 is a schematic diagram of a measurement apparatus according tosome embodiments.

FIG. 5 is a diagram of a process to determine a temperature according tosome embodiments.

FIG. 6 is a diagram of a system according to some embodiments.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of IC die portion 100 according to someembodiments. IC die portion 100 includes integrated electrical devicesand may be fabricated using any suitable substrate material andfabrication techniques. IC die portion 100 may provide one or morefunctions in addition to those described herein. In some embodiments, ICdie portion 100 is a portion of a microprocessor die having a siliconsubstrate.

IC die portion 100 includes temperature sensor 110, amplifier 120,current mirror 130 and disable circuit 140. Temperature sensor 110 mayoperate to sense a temperature of IC die portion 100, and amplifier 120may output the sensed temperature to an external system as voltage VT.More specifically, current devices 112 of temperature sensor 110 maybias diode(s) 114, and a voltage associated with biased diode(s) 114 maybe transmitted to amplifier 120. The voltage transmitted to amplifier120 as well as voltage VT may have a known mathematical relationship toa temperature of IC die portion 100, therefore the temperature may bedetermined therefrom.

Current mirror 130, disable circuit 140 and memory 150 may operateduring and after calibration of temperature sensor 110. According tosome embodiments, disable circuit 140 may disable current devices 112 soas to prevent current devices 112 from biasing diodes 114. During suchdisabling, current mirror 130 receives current I_(EXT) from an off-diecurrent source (not shown) and biases diode(s) 114 using the currentI_(EXT). Depending on the configuration of current mirror 130, diode(s)114 may be biased by current I_(EXT) or by a known fraction or knownmultiple of current I_(EXT).

As described above, amplifier 120 receives a voltage associated withbiased diode(s) 114, and the voltage may be used to determine atemperature of IC die portion 100. The value of current I_(EXT) anddiode(s) 114 may be controlled to a high degree according to someembodiments. Therefore, the temperature determined according to theabove-described calibration procedure may be more accurate than thetemperature determined using current devices 112.

According to some embodiments, an ambient temperature surrounding IC dieportion 100 is held constant while two temperatures are determined usingthe processes described above. A difference between the two determinedtemperatures is then determined and stored in memory 150. The storeddifference may then be used to correct a temperature that issubsequently determined using current devices 112.

FIG. 2 is a flow diagram of process 200 according to some embodiments.Process 200 may be used to determine a temperature of an IC dieaccording to some embodiments. Process 200 may be implemented by anysuitable combination of hardware, software, and firmware, including butnot limited to implementations of IC die portion 100.

At 210, current from an off-die current source is used to bias diodes ofa temperature sensor disposed in an IC die. Referring to the FIG. 1example, current mirror 130 receives current I_(EXT) from an off-diecurrent source and biases diode(s) 114 using the current I_(EXT) at 210.

Next, at 220, a voltage is generated based on the current and on atemperature of the IC die. The voltage may be generated by the biaseddiodes. In other words, the current is used to bias the diodes and aresponse of the diodes is influenced by a temperature of the IC die.Accordingly, a voltage generated by the diodes is based both on thereceived current and on the temperature of IC die portion 100.

A first temperature is determined based on the voltage at 230. Accordingto some embodiments, the first temperature is determined based on amathematical relationship between the current applied to the diodes,electrical characteristics of the diodes, and a temperature of thediodes. Since the applied current and the electrical characteristics maybe known and controlled to a substantial degree, the first temperaturemay be determined more accurately and efficiently than in previoussystems.

FIG. 3 is a schematic diagram of a portion of IC die 300 according tosome embodiments. IC die 300 includes diodes 314, amplifier 320 andcurrent mirror 330. Diodes 314, amplifier 320 and current mirror 330 maycomprise implementations of diode(s) 114, amplifier 120 and currentmirror 130, respectively, of FIG. 1. Moreover, IC die 300 may also oralternatively implement process 200 according to some embodiments.

Current mirror 330 comprises p-channel metal-oxide semiconductor (PMOS)transistor 332 to receive current I_(EXT) from an off-die currentsource. This current is mirrored by PMOS transistors 334 and 336 inproportions that depend on the relative sized of PMOS transistors 332,334 and 336. Transistors 334 and 336 bias diodes 315 and 316 using themirrored current. The resulting difference in voltage drops acrossdiodes 315 and 316 is shown as voltage V_(dt).

Voltage V_(dt) is received by amplifier 320, which in turn generatesvoltage V_(Adt). Amplifier 320 includes oscillator 322 and chopperstabilizer 324. In operation, oscillator 322 oscillates between twostates (e.g., “1” and “0”) at a relatively low frequency, causingchopper stabilizer 324 to output a first voltage V_(Adt1), associatedwith a first state of oscillator 322 and a second voltage V_(Ad2t)associated with a second state of oscillator 322.

A temperature T of IC die 300 may be determined based on the followingequation:

${T = {\frac{R}{R_{F}}\left( \frac{q}{n\; \ln \; \sigma \; k} \right)V_{Adt}}},$

where V_(Adt)=|V_(Adt1)−V_(Ad2t)|/2, k corresponds to Boltzmann'sConstant, n corresponds to an ideality factor associated with diodes314, and q corresponds to the charge of a electron. In some embodiments,n=1 for most IC fabrication technologies and n=2 for discretecomponents. Particular values used for the other variables may varydepending upon desired degrees of accuracy and/or preferred units.

FIG. 4 is a schematic diagram of a portion of IC die 400 according tosome embodiments. IC die 400 includes current devices 412, diodes 414,amplifier 420, disable circuit 440, binary flash analog/digitalconverter 450 and multiplexer 460. Current devices 412, diodes 414,amplifier 420, disable circuit 440, and binary flash analog/digitalconverter 450 may comprise implementations of current devices 112,diode(s) 114, amplifier 120, disable circuit 140, and memory 150,respectively, of FIG. 1.

Disable circuit 440 may operate to enable or disable current devices 412based on a received Enable signal. When enabled, current devices 412bias diodes 414 and voltage V_(dt) represents the resulting differencein voltage drops across diodes 415 and 416. Amplifier 420 receivesvoltage V_(dt) and generates voltage V_(Adt) based thereon. According tosome embodiments, amplifier 420 alternately outputs a first voltageV_(Adt1) and a second voltage V_(Ad2t) to multiplexer 460 andmultiplexer 460 outputs V_(Adt)=|V_(Adt1)−V_(Ad2t)|/2.

A temperature T of IC die 400 may therefore be determined based on thefollowing equation:

${V_{Adt} = {{\frac{R_{F}}{R}\left( \frac{n\; \ln \; \sigma \; {sk}}{q} \right)T} + {\frac{R_{F}}{R}\left( \frac{n\; \ln \; \sigma \; {sk}}{q} \right)273.15} - {\frac{R_{F}}{R_{s}}\left( V_{DD} \right)}}},$

where V_(Adt)=|V_(Adt1)−V_(AD2t)/2, k corresponds to Boltzmann'sConstant, n corresponds to an ideality factor associated with diodes414, q corresponds to the charge of a electron, and n=1 for most ICfabrication technologies and n=2 for discrete components.

According to some embodiments, IC die 300 and IC die 400 are a same die,and temperatures are determined as described above while the die ismaintained in a substantially constant ambient temperature. Moreover, adifference is determined between the two determined temperatures and thedifference is used to correct temperatures that aresubsequently-determined by the elements of FIG. 4.

In some embodiments, a single amplifier is used for both types oftemperature determination described above. For example, element 330 ofFIG. 3 may be connected to a single amplifier and diodes and disposed inparallel with elements 412 and 440 of FIG. 4, which are also connectedto the single amplifier and diodes.

FIG. 5 is a flow diagram of process 500 according to some embodiments.Process 500 may be used to determine a temperature of an IC dieaccording to some embodiments. Process 500 may be implemented by anysuitable combination of hardware, software, and firmware, including butnot limited to implementations of IC die portion 100, IC die 300 and ICdie 400.

At 505, current from an off-die current source is used to bias diodes ofa temperature sensor disposed in an IC die. Referring to FIG. 3, PMOStransistor 332 receives current I_(EXT) from an off-die current source.The received current is mirrored by PMOS transistors 334 and 336 todiodes 315 and 316 in proportions that depend on the relative sized ofPMOS transistors 332, 334 and 336. Assuming that elements 314 and 330 ofFIG. 3 are disposed in parallel with elements 412, 414 and 440 asdescribed above, 505 may also comprise disabling current devices 412using the Enable signal.

Next, at 510, a voltage is generated based on the current and on atemperature of the IC die. The generated voltage may comprise thedifference in voltage drops across diodes 315 and 316. This voltage isbased both on the received current and on the temperature of IC die 300.

The generated voltage is amplified using an oscillator and a chopperstabilizer at 515. In the present example, voltage V_(dt) is receivedand amplified by oscillator 322 and chopper stabilizer 324 of amplifier320. In addition, a first amplified voltage associated with a firststate of the oscillator and a second amplified voltage associated with asecond state of the oscillator are determined at 520. For example,chopper stabilizer 324 outputs a first voltage V_(Adt1) associated witha first state of oscillator 322 and a second voltage V_(Ad2t) associatedwith a second state of oscillator 322.

A third voltage is determined at 525 based on the first and secondamplified voltages. The third voltage V_(Adt) may be equal to|V_(Adt1)−V_(Ad2t)|/2. The third voltage may be determined by on-die oroff-die systems. An on-die or off-die system may determine a firsttemperature based on the third voltage at 530. According to someembodiments, the temperature is determined based on the equationprovided above:

$T = {\frac{R}{R_{F}}\left( \frac{q}{n\; \ln \; \sigma \; k} \right){V_{Adt}.}}$

A second temperature is determined using the temperature sensor at 535.As described above, the second temperature may be determined using thesame diodes and amplifier as used in 505 through 520. As an example ofsuch a case, disable circuit 440 may operate at 535 to enable currentdevices 412 based on a received Enable signal. Current devices 412therefore bias diodes 414 and voltage V_(dt) represents the resultingdifference in voltage drops across diodes 415 and 416. Amplifier 420 mayreceive voltage V_(dt) and generate voltage V_(Adt) based thereon asdescribed above. The third temperature T may therefore be determined at535 based on the following:

$V_{Adt} = {{\frac{R_{F}}{R}\left( \frac{n\; \ln \; \sigma \; {sk}}{q} \right)T} + {\frac{R_{F}}{R}\left( \frac{n\; \ln \; \sigma \; {sk}}{q} \right)273.15} - {\frac{R_{F}}{R_{s}}{\left( V_{DD} \right).}}}$

A temperature correction value is determined at 540 based on the secondtemperature determined at 535 and the first temperature determined at530. According to some embodiments, the temperature correction value issubstantially equal to a difference between the first and secondtemperatures. Determination of the correction value at 540, in someembodiments, assumes that an ambient temperature surrounding the IC dieis substantially constant from 505 through 535.

The temperature correction value is stored at 545. For example, thefirst temperature may be 26.34 degrees Celsius and the secondtemperature may be 26.85 degrees Celsius. The temperature correctionvalue may therefore be determined as 26.34−26.85=−0.51 according to someembodiments. In some embodiments of 545, the temperature correctionvalue is burned into fuses or other Read Only Memory of the IC die.

At 550, a third temperature is determined using the temperature sensor.The third temperature may be determined as described above with respectto determination of the second temperature. A fourth temperature is thendetermined at 555 based on the third temperature and the storedtemperature correction value. Continuing with the above example, thethird temperature may be determined to be 28.45 degrees Celsius at 550,and the fourth temperature may be determined to be 28.45+(−0.51)=27.94degrees Celsius at 550. In some embodiments, 505 through 545 occur priorto shipping the IC die to an end-user, and 550 through 555 occur duringuse of the IC die by the end-user.

FIG. 6 illustrates a block diagram of system 600 according to someembodiments. System 600 includes microprocessor 610 comprising IC dieportion 100 of FIG. 1. Microprocessor 610 communicates with off-diecache 620 according to some embodiments.

Microprocessor 610 may communicate with other elements via a host busand chipset 630. Chipset 630 also communicates with memory 640, whichmay comprise any type of memory for storing data, such as a Single DataRate Random Access Memory, a Double Data Rate Random Access Memory, or aProgrammable Read Only Memory. Other functional units, such as graphicscontroller 650 and Network Interface Controller (NIC) 660, maycommunicate with microprocessor 610 via appropriate busses or ports.

The several embodiments described herein are solely for the purpose ofillustration. The various features described herein need not all be usedtogether, and any one or more of those features may be incorporated in asingle embodiment. Some embodiments may include any currently orhereafter-known versions of the elements described herein. Therefore,persons skilled in the art will recognize from this description thatother embodiments may be practiced with various modifications andalterations.

1. A method comprising: biasing diodes of a temperature sensor disposed in an integrated circuit die using a current from an off-die current source; generating a voltage based on the current and a temperature of the integrated circuit die; and determining a first temperature based on the voltage.
 2. A method according to claim 1, further comprising: amplifying the voltage using an oscillator and a chopper stabilizer; determining a first amplified voltage associated with a first state of the oscillator and a second amplified voltage associated with a second state of the oscillator; and determining a third voltage based on the first amplified voltage and the second amplified voltage, wherein determining the first temperature based on the voltage comprises determining the first temperature based on the third voltage.
 3. A method according to claim 2, wherein determining the third voltage comprises determining (|first amplified voltage−second amplified voltage|)/2.
 4. A method according to claim 1, wherein biasing the diodes comprises: receiving the current at a current mirror; and outputting current from the current mirror to the diodes.
 5. A method according to claim 1, further comprising: determining a second temperature using the temperature sensor; and determining a temperature correction value based on the second temperature and the first temperature.
 6. A method according to claim 5, wherein the temperature correction value equals a difference between the second temperature and the first temperature.
 7. A method according to claim 5, further comprising: storing the temperature correction value; determining a third temperature using the temperature sensor; and determining a fourth temperature based on the third temperature and the temperature correction value.
 8. An integrated circuit die comprising: a temperature sensor comprising a plurality of current devices and at least one diode, the plurality of current devices to bias the at least one diode; a first circuit to disable the plurality of current devices; a current mirror to receive a current from an off-die current source and to bias the at least one diode using the current in a case that the plurality of current devices are disabled; and an amplifier to generate a voltage based on the at least one biased diode, wherein a first temperature of the integrated circuit die may be determined based on the voltage.
 9. An integrated circuit die according to claim 8, wherein the amplifier comprises an oscillator and a chopper stabilizer, wherein the amplifier is to output a first amplified voltage associated with a first state of the oscillator and a second amplified voltage associated with a second state of the oscillator; and wherein determination of the first temperature of the integrated circuit die includes a determination of a third voltage based on the first amplified voltage and the second amplified voltage, and determination of the first temperature based on the third voltage.
 10. An integrated circuit die according to claim 9, wherein determination of the third voltage comprises a determination of (|first amplified voltage−second amplified voltage|)/2.
 11. An integrated circuit die according to claim 8, wherein the temperature sensor is to determine a second temperature, and wherein the second temperature and the first temperature may be used to determine a temperature correction value.
 12. An integrated circuit die according to claim 11, wherein the temperature correction value equals a difference between the second temperature and the first temperature.
 13. An integrated circuit die according to claim 1 1, further comprising: a memory to store the temperature correction value, wherein the temperature sensor is to determine a third temperature; and wherein the temperature sensor is to determine a fourth temperature based on the third temperature and the temperature correction value.
 14. A system comprising: a microprocessor comprising: a temperature sensor comprising a plurality of current devices and at least one diode, the plurality of current devices to bias the at least one diode; a first circuit to disable the plurality of current devices; a current mirror to receive a current from an off-die current source and to bias the at least one diode using the current in a case that the plurality of current devices are disabled; and an amplifier to generate a voltage based on the at least one biased diode; and a double data rate memory, wherein a first temperature of the microprocessor may be determined based on the voltage.
 15. A system according to claim 14, wherein the amplifier comprises an oscillator and a chopper stabilizer, wherein the amplifier is to output a first amplified voltage associated with a first state of the oscillator and a second amplified voltage associated with a second state of the oscillator; and wherein determination of the first temperature of the integrated circuit die includes a determination of a third voltage based on the first amplified voltage and the second amplified voltage, and determination of the first temperature based on the third voltage.
 16. A system according to claim 15, wherein determination of the third voltage comprises a determination of (|first amplified voltage−second amplified voltage|)/2.
 17. A system according to claim 14, wherein the temperature sensor is to determine a second temperature, and wherein the second temperature and the first temperature may be used to determine a temperature correction value.
 18. A system according to claim 17, wherein the temperature correction value equals a difference between the second temperature and the first temperature.
 19. A system according to claim 17, further comprising: a memory to store the temperature correction value, wherein the temperature sensor is to determine a third temperature; and wherein the temperature sensor is to determine a fourth temperature based on the third temperature and the temperature correction value. 